Article clearly explains that Tesla does not break out region sales, just world wide quarterly sales, so this number is an informed estimate.
When the news is good, you shout it from the rooftops. When the news is bad, well, you do what is legally required by the SEC.
Other manufacturers sell through dealers, Tesla doesn't.
In other words, for other manufacturers there are several places in the supply chain to get the numbers from. For Tesla, the only place to get numbers is from Tesla itself.